Refrigeration system



Feb. 6, 1968 w. MCGRATH 3,367,125

REFRIGERATION SYSTEM Filed Sept. 2, 1966 E I? I4 E I O O O O O O O O O20 O O O O VZI INVENTOR.

WILLIAM L. MCGRATH.

ATTORNEY.

United States Patent 3,367,125 REFRIGERATION SYSTEM William L. McGrath,Syracuse, N. assignor to Carrier Corporation, Syracuse, N.Y., acorporation of Delaware Filed Sept. 2, 1966, Ser. No. 576,899 4 Claims.(Cl. 62-116) This invention relates to a refrigeration system and amethod of providing refrigeration and, more particularly, to a methodand circuit for improving the efliciency of a refrigeration system.Refrigerant gas, such as a portion of the economizer flash gas, which ina sense may be considered a loss as far as refrigerating effect isconcerned, is utilized to lift the remainder of the economizer flash gasto the high pressure side of the system so that the energy of the gas isutilized to improve the efficiency of the system.

In the past it has been proposed to expand refrigerant in an expansionmotor prior to passing it into an evaporator, the expansion motor beingused to drive a refrigerant compressor or perform other work in thesystem. While such expedients may provide advantages in a refrigerationsystem, for the most part they do not utilize the energy in an efflcientmanner.

It is a primary object of this invention to provide a new and improvedrefrigeration system and method of providing refrigeration.

An important object of this invention is to increase the efficiency of arefrigeration system.

A further object of this invention is to increase the efficiency of arefrigeration system employing a single stage centrifugal compressor.

Another object is the provision of a new and improved refrigerationsystem in which refrigerant gas compression means is driven by a portionof the flash gas in the system for lifting the remainder of the flashgas to a relatively high side of the system so that the energy of theflash gas is utilized to improve the efiiciency of the system. A relatedobject is provision in a refrigeration system having an economizer, fordriving refrigerant gas compression means with economizer flash gas.

Another object is to provide a new and improved method of increasing theefficiency of a refrigeration system wherein a portion of the flash gasin the system is utilized for driving a compressor which liftsrefrigerant vapor to a relatively high side of the system, therebyutilizing the energy of the flash gas to improve the efliciency of thesystem.

The invention is embodied in a small turbocompressor which is driven byrefrigerant gas in the system, for example, economizer flash gas. Aportion of the flash gas is expanded in the turbocompressor anddischarged into an evaporator while the remainder of the flash gas islifted from the economizer to the refrigerant condenser. While theinvention is equally applicable to heat pumps, absorption refrigerationsystems and other types of refrigeration systems, it is illustrated in acompression type refrigeration system with the turbocompressor and asingle stage main refrigerant compressor. With the arrangementillustrated, the pressure drop across the turbine section of theturbocompressor is of the same magnitude as the lift of the compressorsection thereof, allowing the turbine wheel and compressor wheel to beaerodynamically matched and therefore highly eflicient.

Refrigeration systems employing the economizer principle wherein theliquid refrigerant formed in the condenser is passed to an economizerchamber having com munication with an intermediate stage of a multistagecompressor so as to be at a pressure intermediate the high and lowpressure sides of the system are utilized to cool water for use in airconditioning installation for 3,367,125 Patented Feb. 6, 1968 "Ice largebuildings. The use of an economizer with single stage refrigerantcompressors has heretofore been limited due to the difficultyencountered inv efiiciently utilizing the intermediate pressureeconomizer gas.

This invention contemplates, in its preferred form, using a portion ofthe flash gas formed as the liquid refrigerant flowing from thecondenser enters the economizer chamber, as a power fluid for driving aturbocompressor, the compressor portion of which is connected betweenthe economizer and the condenser of the refrigeration system for thepurpose of delivering a portion of the gas generated in the economizerto the condenser and expanding the remainder through the turbine sectionof the turbocompressor to the evaporator. Turbocompressors of the kindunder consideration are often used as superchargers for internalcombustion engines.

The attached drawing is a flow diagram of a refrigeration systemincorporating the arrangement illustrating a preferred embodiment of theinvention.

In the drawing, a first or main compressor 11 of any desired type isdriven by a suitable means such as an electrical motor or a turbine 11',and receives refrigerant vapor through a main suction line 12 from anevaporator 13 and passes compressed refrigerant through a main dischargeline 14 to a refrigerant condenser 15. From the condenser 15 therefrigerant flows through a condensate line 16 to refrigerant flowcontrol means, here in the form of an economizer 17 for sub-cooling therefrigerant. The economizer has a first valve 18 which receives thecondensed refrigerant and passes the refrigerant into an economizerchamber 19 for collecting economizer flash gas and from which the flashcooled refrigerant passes through a second valve 20 and an evaporatorsupply line 21 into the evaporator 13 provided with a chilled water line22 to a load to be cooled. From the evaporator the vaporized refrigerantenters the suction line 12 thus completing the refrigerant circuit.

A refrigerant economizer circuit includes a second or auxiliaryrefrigerant compressor, preferably a centrifugal turbocompressor 30,which is connected in parallel with the main compressor 11 between theeconomizer 17 and the condenser 15. More particularly, line 31 betweeneconomizer 17 and turbocompressor 30 passes refrigerant vapor from theeconomizer to the turbine section 30A and the compressor section 30B ofturbocompressor 30, the refrigerant compressed by compressor section 30Bpassing to the refrigerant condenser 15 through line 32 and therefrigerant vapor expanded through turbine section 30A passing to theevaporator 13 through line 33.

The refrigerant flash gas in the economizer chamber 19 is at anintermediate pressure between that of the high pressure side of thesystem (between the discharge of the main compressor 11 and the valve18) and the low pressure side of the system (between the second valve 20and the suction of the main compressor 11) so that the flash gas drivingthe turbine passes from a zone of intermediate pressure within theeconomizer chamber 19 to a zone of low pressure within the evaporator13, while the flash gas being compressed passes from a zone ofintermediate pressure within the economizer chamber 19 to a zone of highpressure within condenser 15. By passing only gas to the turbine,cavitation of the turbine is effectively prevented.

It is to be understood that a turbine drivingly connected to acompressor could be used in place of the turbocompressor 30. However, aturbocompressor does offer a few distinct advantages. Because both theturbine and compressor sides of the turbocompressor are passing the samefluid, that is, refrigerant, it is not necessary to provide relativelytight seals between the turbocompressor sections, and the shaft 37mounted in any suitable type of bearings can be lubricated by therefrigerant gas therein.

The economizer circuit is self-balancing since it is driven by flash gasand compresses flash gas. The capacity of the turbocompressor isgoverned by the supply of economizer gas generated in the refrigerationcircuit. Accordingly, at low lifts the speed and thus the pumpingcapacity of the turbocompressor is relatively low. At high lifts whenadditional pumping capacity is desirable, the turbocompressor operatesat higher speeds thus rendering additional capacity to the maincompressor. Because of the relationship between the turbocompressorperformance and the refrigeration system operating condition asindicated by the economizer gas, the turbocompressor can improve cycleefficiency without special controls such as suction guide vanes,throttling valves or the like. Because of the simplicity of this system,the turbocompressor portion thereof may be provided as an accessory onany existing refrigeration systems employing a condenser and evaporatorand automatically balances to any particular operating condition of thesystem.

Another advantage obtained with the turbocompressor unit is realized inheat pump applications where an increased lift is required whenoperating during the heating cycle. The turbocompressor will assist themain compressor so that a smaller and less expensive main compressor maybe employed.

Another advantage of the proposed system incorporating an economizer andturbocompressor is its applicability to single stage compression systemsto provide single stage system elficiency comparable to two stagesystems.

Still another advantage is the efiiciency of the turbocompressor whenutilized in the manner described. By providing a pressure drop acrossthe turbine section thereof of comparable magnitude with the lift on thecompressor section, the turbocompressor efliciency can be optimized.

While a preferred embodiment of the invention has been described andillustrated, it will be understood that the invention is not limitedthereto since it may be otherwise embodied within the scope of thefollowing claims.

I claim:

1. A method of improving the efficiency of a refrigeration systemincluding a relatively low pressure refrigerant evaporator, a relativelyhigh pressure refrigerant condenser and a refrigerant compressor havinga prime mover drivingly connected thereto comprising the steps of:passing refrigerant from the evaporator to the condenser, expandingliquid refrigerant passing from the condenser to the evaporator, therebycreating flash gas atan intermediate pressure and cooling the liquidrefrigerant passing to said evaporator to improve the efficiencythereof, passing a portion of the flash gas to the prime mover fordriving the compressor, passing the remainder of the flash gas to thecompressor, and passing the compressed flash gas from the compressor tothe condenser, thereby utilizing the energy of the flash gas to improvethe efficiency of the system.

2. A refrigeration system comprising a relatively low pressureevaporator, a relatively high pressure condenser, a refrigerantcompressor for lifting refrigerant from an intermediate pressure portionof the system to said condenser and means for driving said compressor byexpanding refrigerant gas from an intermediate pressure to evaporatorpressure.

3. A refrigeration system according to claim 2 wherein said means fordriving said compressor comprises a turbine operatively connectedthereto.

4. A refrigeration system according to claim 3 further including aneconomizer, means for passing a portion of the economizer gas to saidcompressor for lifting economizer gas to the condenser, and means forpassing a portion of the economizer gas to said turbine for expansiontherethrough.

References Cited UNITED STATES PATENTS LLOYD L. KING, Primary Examiner.

2. A REFRIGERATION SYSTEM COMPRISING A RELATIVELY LOW PRESSUREEVAPORATOR, A RELATIVELY HIGH PRESSURE CONDENSER, A REFRIGERANTCOMPRESSOR FOR LIFTING REFRIGERANT FROM AN INTERMEDIATE PRESSURE PORTIONOF THE SYSTEM TO SAID CONDENSER AND MEANS FOR DRIVING SAID COMPRESSOR BYEXPANDING REFRIGERANT GAS FROM AN INTERMEDIATE PRESSURE TO EVAPORATORPRESSURE.